Approximately 1700 kindergarten and first grade children were randomly assigned to one of the following groups: Group I - Rinses once every week in school with a 0.2% fluoride solution. Group III - Ingests once a day in school a sodium fluoride tablet containing 1 mg of fluoride. Group II - Carries out the regimens for both Group I and Group III. The method of assignment resulted in three comparable groups, each containing about 560 children. Participants carry out their assigned treatments in classrooms under the supervision of a teacher. Treatments will be administered for a minimum of eight years. Baseline dental examinations were conducted in September 1981. The prescribed treatments were initiated shortly after the examinations were completed. In September 1985, the fifth school year of treatments began in the classrooms. First follow-up dental examinations were made in October 1983 of 1,154 participants who were then in grades 2 and 3. Supplies have been ordered, schedules arranged and local personnel identified for the start-up of the sixth school year of treatments in September 1986.